What is HTTPS and what does it do?

HTTPS takes the well-known and understood HTTP protocol, and simply layers a SSL/TLS (hereafter referred to simply as “SSL”) encryption layer on top of it. Servers and clients still speak exactly the same HTTP to each other, but over a secure SSL connection that encrypts and decrypts their requests and responses. The SSL layer has 2 main purposes:

• Verifying that you are talking directly to the server that you think you are talking to
• Ensuring that only the server can read what you send it and only you can read what it sends back

The really, really clever part is that anyone can intercept every single one of the messages you exchange with a server, including the ones where you are agreeing on the key and encryption strategy to use, and still not be able to read any of the actual data you send.